Figure 2. Methodology used to demonstrate tumour invasion by histological sectioning (haematoxylin and eosin (H&E) and fluorescent labelled images). Upper row: Human dermal fibroblasts (HDFs) are seen on top of the ectoderm together with the extracellular matrix (ECM) (arrow heads) they have produced. The ectoderm of the CAM (red arrows) can clearly be followed underneath the HDF and ECM layer demonstrating noninvasion. Corresponding fluorescent micrographs confirm the presence of green fluorescent labelled HDFs on top of the ectoderm (red arrows), with no presence of HDFs in the mesoderm. Lower row: Human melanoma cells (C8161) can be seen as an aggregate (arrow head) on top of CAM extending from the surface to the mesoderm in H&E sections. The ectoderm-mesoderm border (red arrows) is destructed (black arrows). Corresponding fluorescent images confirm presence of fluorescently labelled tumour cells in the mesoderm of the CAM (green labelling/white arrow head) with disruption of the ectoderm-mesoderm border (red arrows) confirming invasion (see inset).